On 12/19/2006 4:16 PM, Benjamin Tyner wrote: > Thanks; I'm on 32-bit linux, but it's good to know the behavior on > Windows. Do you know a way to force "floor" to use this reduced precision?
Force the value to be stored to a "double" and it will get the reduced precision. You can do this by assigning it to a numeric variable in R and then passing it back; you can presumably do it by some trickery in your compiler, but watch out for optimizations that leave it in an 80 bit register the whole time. Duncan Murdoch > > Ben > > Duncan Murdoch wrote: >> On Windows, it's fairly common for runtime libraries to switch the >> precision from 80 bit to 64 bit. R on Windows tries to guard against >> this, and on your test package, I get >> >> when f computed by R, C says 40 by itself >> when f computed by R, C says 40, Fortran says 40 >> when f computed by C, C says 40 by itself >> when f computed by C, C says 40, Fortran says 40 >> >> It's possible that the floating point change is happening on your >> platform, or happened before you even got to this call. >> >> Here's code that works in Windows to detect such a change across a >> LoadLibrary call: >> >> rcw = _controlfp(0,0) & ~_MCW_IC; /* Infinity control is ignored */ >> _clearfp(); >> tdlh = LoadLibrary(path); >> dllcw = _controlfp(0,0) & ~_MCW_IC; >> >> No idea if _controlfp() exists on your system. >> >> Duncan Murdoch ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
